Glass compositions



GLASS COMPOSITIONS Frederick R. Rogers, Hornby, N. Y., assignor to Vitreous Research Corporation, Painted Post, N. Y., a corporation of New York No Drawing. Application March 23, 1950, Serial No. 151,521

8 Claims. (Cl. 106-53) This invention relates to glass compositions, and more particularly, to castable glasses which are adapted for use in glass-to-metal seals.

The primary object of my invention is to provide new castable glass compositions having low working temperatures, low coefiicients of expansion, and high fluidity at low temperatures.

Another object of my invention is to provide improved hermetic glass seals with metals having low coeflicients of expansion in the range of about 45 to 70x10 I cal proportions which may be conveniently divided into three sub-groups as follows: (1) Those compositions which correspond essentially to the following formulations expressed in per cent by weight: 30 to 65% Al(BO2)3; and 5 to 40% of at least one divalent metaborate of the group consisting of Ba(BO2)2, Ca(BOz)2, Sr(BO2)z and Pb(BO2) 2 (2) Those compositions in which the Al(BOz)3 is replaced in part by either or both Z11(BO2)2 and Mg(BO2)2- in an amount of up to 25% of each of the latter two metaborates. However, there must be at least 10% Al(BOz)3 present in such a case and the total amount of this first group must still be between 30 and 65%. (3) Those compositions of subgroups (1) and (2) which also contain 5 to 30% of metaborates of the group consiting of NaBOz, KBOz and LiBOz. When Zn(BO2)2 and/or Mg(BO2)2 are present in the glass, I prefer that they constitute at least 5% by weight of the final glass.

The oxide percentages corresponding to the metaborate percentages recited in the three sub-groups are given below.

Sub-group I Al(BO2)a A1203 320a 30 9. 8 20. 1 65 21. 3 43. 7 B3,(B O2): BaO B203 5 3. 4 1. 6 40 27. 5 12. 5 Ca(BO2)2 02.0 13203 5 2. 2 2. 8 40 17.8 22.2 Pb(BO2)2 Pbo B203 5 3. 8 1. 2 40 S 030. 5 B O 9. 5 S1 BO 2 l 2 a Sub-group II A1(BOz) A1203 B203 10 3. 3 6. 7 60 19. 6 40. 4 ZD(BO2)2 ZnO B205 5 2. 7 2. 3 25 13. 4 I1. 6 Mg(BO2)2 MgO B203 Sub-group III NaIB O2 N820 B203 5 2. 3 2. 65 3O 14. 10 15. KB Oz K20 1320:

5 2. 8 2.2 30 16.8 13. 2 LIB Oz LizO B203 In order to obtain certain specific and desirable characteristics in the glasses, it has been found that other oxides may be added to the parent metaborate glass without impairing the essential properties of the glass. These oxides dissolve in the metaborate glass and become an integral part thereof. Other oxides which may be used and their maximum percentages by weight based on the final glass are as follows: SiOz up to 20%, A1203 up to 10%, SnOz up to 2%, TiOz up to 10% and ZnO up to 10%. I prefer those glasses in which there is at least 5% by weight of SiOz. The total amount of such oxides preferably does not exceed 30% by weight of the glass if all the desirable properties of my new glasses are to be obtained.

I have found that the above defined glasses can be readily cast because of their low softening temperatures and high fluidity at moderate working temperatures. They have softening temperatures ranging between about 475 C. and 850 C. They are eminently suited to be cast into intricate shapes. A further advantage of my glasses is the fact that they fine readily without the necessity of special fining agents. They exhibit little tendency to become cordy. Another advantage is the stability of the melt at Working temperatures. These glasses are not easily volatilized at convenient casting temperatures.

For the above and other reasons the glasses of the present invention are especially suited for the manufacture of glass-to-metal seals wherein the metal or alloy has a coeificient of expansion in the range of 45 to 70 l0 in the range of 20-300 C. Because of their castability they serve particularly well in the manufacture of the larger types of hermetic seals, especially with multiple electrodes, and insulator bushings with metal inserts. Owing to the low temperature at which the glasses can be cast, there is no spattering of ferrous metal when an iron alloy is heated to the sealing temperature. I have further found that these glasses are consistently uniform in their properties from melt to melt which promotes economical manufacturing.

In Table I examples of my new compositions falling within the scope of this invention are given in terms of weight per cent as calculated from their respective batches.

TABLE I Glass A1(B02)3 3 ZIl(BO2)E-- SnOz Mg(BOn)2 A1203 Goef. Exp. X 10 Annealing Temp., 0..-- Softening Temp., 0

In the following Table II are given the oxide analyses of the glasses in Table I.

TABLE II B O D E In the following Table III are given the batch compositions in parts by weight of the glasses appearing in Table I.

TABLE III I have found that glasses corresponding substantially to glass A in the above tables serve extremely well in the manufacture of hermetic glass-to-metal seals with No. 42 Alloy, which comprises approximately 42% by weight of nickel, the balance being iron. The percentage composition of the ingredients of glass A may be varied from 1 to 3 per cent either way and yet seal effectively to Alloy No. 42.

According to the provisions of the patent statutes, I have explained the principle, preferred construction, and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. A glass composition consisting essentially of 30 to 65% by weight of a mixture of metaborates consisting of Al(BO2)3 and at least one metaborate of the group consisting of Zn(BO2)2 and Mg(BO2)2, the Al(BO2)3 being present in the amount of at least 10% by weight and M the Zn(BO2)2 and Mg(BO2)2, when present, being in an amount between 5 and 25% by weight respectively; 5 to 40% by weight of at least one divalent metaborate of the group consisting of Ba(BO2)2, Ca(BO2)2, Sr(BOz)2, and Pb(BO2)2; and containing 5 to 30% by weight of at least one metaborate of the group consisting of NaBO2, K1302 and LiBOz, and from 5 to 20% by weight of SiOz.

2. A glass composition consisting essentially of 10 to 60% by weight of AI(BO2)3, 5 to 25% by weight of Zn(BO2)2, the sum total of said metaborates being between 30 and 5 to 40% by weight of at least one divalent metaborate of the group consiting of Ba(BO2)2, Ca(BO2)z, Sr(BO2)2 and Pb(BO2)2; 5 to 30% by weight of at least one metaborate of the group consisting of lsq aoBOz, K: and LiBOz, and 5 to 20% by weight of 3. A glass composition consisting essentially of 10 to 60% by weight of Al(BO2)3, 5 to 25% by weight of Zn(BO2)2, the sum total of said metaborates being between 30 and 65%; 5 to 40% by weight of Ca(BO2)2; 5 to 30% by weight of at least one metaborate of the group consisting of NaBOz, KBO2, and LiBOz, and 5 to 20% by weight of SiO2.

4. A glass composition corresponding essentially to the following formulation expressed in per cent by weight: 36.2% Al(BO2)3, 11.6% Zn(BO2)2, 20.1% Ca(BO2)2, 6.0% K1302, 10.0% LiBO2, and 16.1% SiOz.

5. A glass composition corresponding essentially to the following formulation expressed in per cent by weight: 34.7% Al(BO2)3, 7.3% Zn(BO2)2, 3.9% KBOz, 11.6% M6302, 3.8% Ba(BO2)2, 23.3% Pb(BO)2, and 15.5% Si 2.

6. A glass composition corresponding essentially to the following formulation expressed in per cent by weight: 33.2% Al(BO2)3, 7.4% Zn(BO2)2, 13.8% Ca(BOz)z, 22.8% Ba(BO2)2, 6.9% Mg(BO2)z and 15.8% SiOz.

7. A glass composition corresponding essentially to the following formulation expressed in per cent by weight: 33.8% Al(BO2)3, 19.7% Zn(BO2)2, 8.4% Ba(BO2)2, 21.1% Pb(BO2)2, and 16.9% SiOz.

8. A glass composition corresponding essentially to the following formulation expressed in per cent by weight: 31.6% Al(BO2)3, 20.8% Ca(BO2)2, 5.9% KBO2, 10.5% kilBgg, 2.5% NaBOz, 16.7% SiO2, 1.7% S1102 and 10.4% 

1. A GLASS COMPOSITION CONSISTING ESSENTIALL OF 30 TO 65% BY WEIGHT OF A MIXTURE OF METABORATES CONSISTING OF AL(BO2)3 AND AT LEAST ONE METABORATE OF THE GROUP CONSISTING OF ZN(BO2)2 AND MG(BO2)2, THE AL(BO2)3 BEING PRESENT IN THE AMOUNT OF AT LEAST 10% BY WEIGHT AND THE ZN(BO2)2 AND MG(BO2)2, WHEN PRESENT, BEING IN AN AMOUNT BETWEEN 5 TO 25% BY WEIGHT RESPECTIVELY; 5 TO 40% BY WEIGHT OF AT LEAST ONE DIVALENT METABORATE OF THE GROUP CONSISTING OF BA(BO2)2, CA(BO2)2, SR(BO2)2, AND PB(BO)2; AND CONTAINING 5 TO 30% BY WEIGHT OF AT LEAST ONE METABORATE OF THE GROUP CONSISTING OF NABO2, KBO2 AND LIBO2, AND FROM 5 TO 20% BY WEIGHT OF SIO2. 